Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Speed responsive
Reexamination Certificate
1999-01-22
2001-10-30
Hannon, Thomas R. (Department: 3682)
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Speed responsive
C474S014000, C474S016000
Reexamination Certificate
active
06309317
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a device for use in a clutch assembly as a centrifugal clutch shifter.
BACKGROUND OF THE INVENTION
High performance engines require quick response times. The drive transmissions must shift speeds quickly to provide optimum performance. This is particularly true in racing situations, for example in snowmobile racing.
The infinitely variable drive pulley for belt drive transmissions commonly found in snowmobile engines is well known. A key part of the clutch system in those transmissions is the actuator lever or shifter which operates as a cam relative to a fixed roller by pivoting about a pivot point on an axially moveable sheave so that in response to centrifugal force the axially moveable sheave of the system is urged towards a axially fixed sheave to thereby transfer rotation to the axially fixed sheave.
Particularly in race conditions, fast clutching and de-clutching is imperative. Therefore, faster response clutches are constantly being pursued. However, the clutches currently being used do not clutch and de-clutch fast enough to provide the racer with optimum performance from the engine. It is believed that these clutches lack the proper weight distribution below the pivot point to provide peak performance throughout the shift.
Attempts to improve clutch performance in the prior art have largely focused on the engagement point of the actuator. For example, U.S. Pat. No. 5,326,330 of Bostelmann, issued Jul. 5, 1994, describes an infinitely variable drive pulley for a belt drive transmission which uses an adjustment eccentric on the adjusting lever of the assembly to adjust the centre of gravity of the lever relative to the pivot pin and the initial position of the cam surface relative to the follower when in the rest or neutral position. This, in theory, varies the engagement speed of the clutch. However, once the clutch is engaged, the weight distribution of the lever does not change as the pulley moves from the rest or neutral position through the shift to the full shift position. Therefore, clutch performance and engine performance are ultimately compromised.
Other attempts at using specialized actuators have been directed toward different clutch assemblies or transmission systems and would therefore not function in the infinitely variable drive pulley system. Reference may be had, for example, to U.S. Pat. No. 771,771 of Dysterud, issued Oct. 4, 1904 and U.S. Pat. No. 2,647,604 of Carmichael, issued Aug. 4, 1953.
There therefore exists a need for a clutch actuator which operates at higher engagement speeds and which allows for weight distribution within the shift.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved device for use in a clutch assembly as a centrifugal clutch shifter.
In one aspect of the invention, there is provided a device for use in a centrifugal clutch assembly in which the clutch assembly comprises a shaft which carries a first sheave axially moveable on the shaft and a second sheave axially fixed on the shaft, a drive belt between the first sheave and the second sheave and a return spring operating on the first sheave. A roller is fixed relative to the first sheave and a pivot pin is fixed on and moveable with the first sheave. The device further comprises a body having an arcuate outer surface constructed so as to provide a cam surface relative to the roller. An aperture is provided in the body and is constructed so as to mate with the pivot pin to allow the device to pivot relative to the pivot pin. A hollow chamber is positioned internally within the body and moveable weighting means are positioned within the chamber. In use, the first sheave rotates at a variable speed, so as to generate a centrifugal force upon the device whereupon at a predetermined engagement speed, the device pivots from a rest position to a full engagement position thereby transferring a force to the first sheave to axially move the first sheave into engagement with the second sheave to transfer rotation from the drive clutch to the secondary clutch.
In another aspect of the invention, there is further provided an adjustment means for adjusting the weighting means within the chamber when the device is in the rest position so as to adjust the engagement speed.
In another aspect of the invention, the weighting means comprises at least one generally spherical member.
In another aspect of the invention, the weighting means comprises fluid filling up to half of the chamber by volume.
REFERENCES:
patent: 771771 (1904-10-01), Dysterud
patent: 2647604 (1953-08-01), Carmichael
patent: 3024886 (1962-03-01), Peras
patent: 3048056 (1962-08-01), Wolfram
patent: 3084775 (1963-04-01), Magnavita
patent: 3165184 (1965-01-01), Hebert
patent: 3283867 (1966-11-01), Rice
patent: 3562224 (1971-02-01), Argereu
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patent: 3939720 (1976-02-01), Aaen et al.
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patent: 5172786 (1992-12-01), Ishibashi
patent: 5280828 (1994-01-01), Reynoso et al.
patent: 5326330 (1994-07-01), Bostelmann
patent: 5328413 (1994-07-01), Robert
patent: 5358450 (1994-10-01), Robert
patent: 5421784 (1995-06-01), Robert
patent: 5458539 (1995-10-01), Landry
patent: 5516332 (1996-05-01), Robert
patent: 5562555 (1996-10-01), Peterson
patent: 5597060 (1997-01-01), Huddleston et al.
patent: 5692982 (1997-12-01), Peterson
patent: 5795255 (1998-08-01), Hooper
patent: 913414 (1972-10-01), None
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patent: 2170970 (1996-11-01), None
patent: 250983 (1948-07-01), None
patent: 85 03800 (1986-09-01), None
Internet material pertaining to Thunder Shift kit, located athttp://www.cloudnet.com~tpi/tskrrl.htm, downloaded Oct. 22, 1997.
Internet article entitled “Why more spring and more weight?”. located athttp://muller.net/karting/docs/technical/clutch1.html, downloaded Oct. 22, 1997.
Charles Marcus
Hannon Thomas R.
Haugen Law Firm PLLP
LandOfFree
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